Eight years from your enlistment ends your statutory obligation.
Six years from your commissioning date ends your contractual obligation, unless you took an incentive that extended that time (e.g., tuition assistance, bonus, school, or other incentive), in which case we'd need to know the details to make a new determination.
These obligations can run concurrently, and can overlap (as yours did, with your statutory obligation ending in 2007, and contractual obligation presumably ending in 2010).
Since you had previous enlisted time, your statutory MSO clock was already running by the time you commissioned.

Comment

Thank you. You are the first person that could clarify this issue for me.I have additional details and would like to mention I have no breaks in service.

I received Federal Tuition Assistance for each year August 2007- August 2009. It was a two years Masters. I found the following reference:

"By law, officers who use TA incur a service obligation. Active Duty officers incur an Active Duty Service Obligation (ADSO) of two years and Reserve Component officers incur a Reserve Duty Service Obligation (RDSO) of four years. The ADSO/RDSO is calculated from the date of completion of the last course for which TA was used. "